Traction arrangement for angularly rotatable sweep auger of circulator grain bins

ABSTRACT

Circulator grain bins commonly comprise upright sidewall means customarily circularly surrounding the bin vertical-axis and also a substantially horizontal floor for supporting a lofty depth of grain thereupon; there is a substantially horizontal elongate sweep auger located immediately above the floor and henced submerged at the bottom of the grain pile, the sweep auger radiating lengthily outwardly from and angularly rotatable about the bin vertical-axis. Each of at least two consecutive medial helical flights for the sweep auger is provided with separate distinct cogs extending radially externally from the flighting helical edge whereby said arrayed distinct cogs at their curved free-edges define a segmented spiroid rim submerged within the grain. A substantially horizontal annular roadway located along the bin floor between the bin sidewall and vertical-axis abuttably underlies the submerged spiroid rim whereby angular rotatation of the axially revolving sweep auger is enhanced and improved to an unusually reliable condition.

United States Patent 1 1 1 Patterson [451 Apr. 2,1974

1 TRACTION ARRANGEMENT FOR ANGULARLY ROTATABLE SWEEP AUGER 0F CIRCULATORGRAIN BINS Primary Examiner-Robert G. Sheridan Attorney, Agent, orFirm-George R. Nimmer [57] ABSTRACT Circulator grain bins commonlycomprise upright sidewall means customarily circularly surrounding thebin vertical-axis and also a substantially horizontal floor forsupporting a lofty depth of grain thereupon; there is a substantiallyhorizontal elongate sweep auger located immediately above the floor andhenced submerged at the bottom of the grain pile, the sweep augerradiating lengthily outwardly from and angularly rotatable about the binvertical-axis. Each of at least two consecutive medial helical flightsfor the sweep auger is provided with separate distinct cogs extendingradially externally from the lighting helical edge whereby said arrayeddistinct cogs at their curved free-edges define a segmented spiroid rimsubmerged within the grain. A substantially horizontal annular roadwaylocated along the bin floor between the bin sidewall and vertical-axisabuttably underlies the submerged spiroid rim whereby angular rotatationof the axially revolving sweep auger is enhanced and improved to anunusually reliable condition.

8 Claims, 7 Drawing Figures PATENTEDAPR 2 w SHEU 1 [IF 2 Circulatorgrain bins basically comprise an upright lofty sidewall meanscustomarily circularly surrounding the bin upright vertical-axis andalso a substantially horizontal floor for supporting bulk grain piledloftily thereupon. Such circulator grain bins also basically comprise anaxially revolvable elongate sweep auger located immediately above andalong the bin floor and hence necessarily submerged at the bottom of thegrain storage pile, the sweep auger radiating axially lengthilyoutwardly from and angularly rotatable about its own elongateauger-axis, and assuming that there are appropriate means to cause thesweep auger to coincidentally angularly rotate about the binvertical-axis, the lowermost horizontal stratum of the entire grain pileis helically fed or swept by the sweep auger toward its inward end,i.e., along the bin floor toward the bin vertical-axis. Grain binsutilizing a helical sweep auger or.

equivalent means for feeding the grain bottom strata toward the binvertical-axis are sometimes generically referred to as circulator grainbins. From the sweep auger inward end, and depending upon whateverspecific type of grain conveyance mechanism is employed thereat, thecirculator grain bin" might have additional means for further conveyanceof the bottom horizontal grain strata. For example, the bottom stratamight be repeatedly re-conveyed or re-cycled within the same bin (suchas within grain dryers, etc.), or conveyed to neighboring bins or othergrain repositories, e.g., so-called grain transferring operations.

Circulator grain bins of larger circular diameters are becoming morepopular for economic or other reasons, which larger bins accordinglyrequire more lengthy rotatable sweep augers. However, with moreelongated lengths for the sweep augers, serious problems can arise. Theprimary problem stems from difficulties encountered in angularlyrotating the not only lengthier, but also heavier, sweep augers aboutthe bin verticalaxis. The helical sweep auger, which is revolvable notobstruct grain flow inwardly along the sweep auger (toward the binvertical-axis). Angular rotation is customarily effected through asuitable drive mechanism which is powerably connected and confined tothe sweep auger inward end. Isolating the auger drive mechanism near thebin vertical-axis has certain engineering advantages, but there areproblems in supplying sufficient torque thereat to make the sweep augersteadily angularly rotate about the bin vertical-axis. Especiallydifficult is the task of powering the sweep auger for angular rotationwhen there is no provision for a so-called vertical auger grainconveyance mechanism extending along the bin vertical-axis and inmeshing engagement with the sweep auger inward end. Such meshingvertical auger conveyors, though very helpful in applying torque to helppowerably rotate the sweep auger, are not always designed into thecirculating grain bin" installation.

It is accordingly the general object of the present invention to providefor angularly rotatable sweep augers of circulator grain bins reasonableassurance in the form of improved traction arrangement that the sweepauger will be made tosmoothly and steadily angularly rotate about thebin vertical-axis as it is being revolved about its auger-axis. It is anancillary general object to provide a traction arrangement or mechanismthat reasonably ensures that the axially revolvable helical sweep augerwill also continuously angularly rotate about the bin vertical-axis andwithout impedance to grain flow axially therealong.

It is another object to provide an improved traction mechanismarrangement for angularly rotatable sweep augers that is adaptable foruse in conjunction with various styles and sizes of floored circulatorgrain bins including those having various grain conveyance meanscommunicating with the sweep auger.

It is a further object to provide a traction arrangement or mechanismfor angularly rotatable sweep augers that is of economical installation,maintenance, and repair, and that is exceedingly reliable in operationfor the intended purposes.

With the above and other objectsand advantages in view, which willbecome more apparent as this description proceeds, the improved tractionarrangement or mechanism for rotatable sweep augers generally comprisesthe provision of a plurality of separate distinct cogs extendingradially externally from the helical edge on consecutive medial flightpitches of the sweep auger to provide a segmented spiroid rim thereforand submerged within the grain, together with a substantially horizontalroadway extending annularly along the bin floor between the sidewall andthe vertical-axis and abuttably underlying the spiroid segmented medialrim support for the auger, whereby traction between the rim and roadwayat the flowing grain interface is achieved and angular rotatability isenhanced.

In the drawing, wherein like characters refer to like parts in theseveral views, and in which:

FIG. 1 is a-sectional elevational view of a representative embodiment ofcirculator grain bin having an angular rotatable sweep anger, theimproved sweeper auger traction means arrangement of the presentinvention being indicated as 50.

FIG. 2 is a sectional plan view taken along line 2'2 of FIG. 1 showingthe entire circular sidewall for the grain bin and the sweep augermedially located improved traction means 50".

FIG. 3 is a sectional elevational view taken along lines 3-3 of FIGS. 1and 2.

FIG. 4 is a sectional elevational view taken along lines 4-4 of FIGS. 1and 2.

FIG. 5 is a sectionalelevational view taken along lines 5-5 of FIGS. 1and 2, and between sectional lines 33 and 44, to show the sweep augertraction means.

FIG. 6 is a detail perspective view of FIG. 5 to show the said coggedspiroid rim for the sweep auger medial portion.

Turning initially to FIGS. 1 and 2 which depict an embodiment 9circulator grain bin (having sweep auger 30) as a representative (thoughnon-limiting) environment for the sweep auger traction arrangement,e.g., 50, of the present invention. The storage bin portion 10 ofembodiment 9 includes upright lofty sidewall means surrounding the binupright vertical-axis 11, the sidewall means herein employed being acircularly tubular sidewall 12. The roof 13 employed herein of the bin10 is of the conventional conical shape. There is a substantiallyhorizontal bin floor 14 spaced above the bin a 3 foundationv 19 whichrests upon the earth E. Bin floor 14, against which the lofty piledgrain (not shown) rests, is multi-perforate as indicated at andcircularly terminates at sidewall 12. Thus, a vigorous stream ofatmospheric or heated air, emerging from heating duct D below bin floor14, can be upwardly ventilated through floor perforations 15 and thencethrough the loftily stored grain to alter the moisture content thereof.Bin floor 14 is also provided with a comparatively large central opening16 (at vertical-axis 11), which floor opening 16 cooperates with thegrain conveyance mechanism, e.g., 20.

By definition, circulator grain bins, e.g., 9, also necessarily comprisea substantially horizontal sweep auger (e.g., 30 having elongateauger-axis 31) located immediately above the bin floor 14 and hence thehelical sweep auger is necessarily submerged at the bottom of the grainstorage pile. Horizontal sweep augers 30 radiate axiallylengthily fromand are also angularly rotatable about the bin vertical-axis 1 1, sweepaugers also being revolvable about the elongate auger-axis 31. Thus,whenever the elongate sweep auger is made to both revolve about its ownauger-axis 31 and to also angularly rotate about the bin vertical-axis11, the lowermost horizontal stratum of the entire grain pile ishelically fed or swept by the sweep auger toward its inward end 33,i.e., along the bin floor 14 toward bin vertical-axis 11. Helicalflighting 35 of several continuous pitches are attached to the sweepauger axial shaft 31T, the helical flighting serving to inwardly sweepthe low- 'ermost grain stratum, As is readily, apparent from the FIG. 2plan view, the grain flow rate appropriately progressively increasestoward the bin vertical-axis 11, the prior art having met thisrequirement in several ways, such as progressively increasing thediameter or reducing the pitch of the helical flighting, etc. In thearbitrarily selected sweep auger 30, the diameter of helical flighting35 progressively increases toward its inward end 33. From the sweepauger inward end 33, the lowermost horizontal grain strata isre-conveyed or recycled depending upon whatever specific type of grainconveyance is employed.

- For circulator grain bin representative embodiment 10, the grainconveyance mechanism selected therefor is a substantially horizontalelongate helical unloader auger 20, which typically also affords themeans for causing the sweep auger 30 to revolve about its augeraxis 31and to also angularly rotate about the bin vertical-axis. Unloader auger20, having external tubular shell 25, is mounted on foundation 19beneath the bin floor 14 and operable herein to convey grain radiallyoutwardly from bin floor central opening 16 exteriorly of the bin. Theunloader auger embodiment 20 comprises a central shaft 21T extendinglongitudinally along its unloader-axis 21. Auger shaft 21T radiates from(but does not angularly rotate about) bin verticalaxis 11, said shaft21T however being revolvable about its own unloader-axis 21. Thus, grainstrata falling downwardly of floor opening 16 can be conveyed exteriorlyof bin 10, such as with auxiliary grain conveyor 200 tiltably associatedwith unloader 20 at 22. The outer end of shaft 21T might be providedwith a pulley 28 and the outer end of tubular shell 25 might be providedwith a motor 26 (having pulley 27), pulleys 27 and 28 being actuatablyconnected with annular belt 29 to effect revolving of shaft 211' aboutunloader-axis 2-1. As is well known in the prior art, the inward end 23of unloader auger shaft 21T might carry a bevel gear (not shown) locatedwithin a gear housing 24 stationarily mounted to foundation 19, and thesweep auger inward end 33 might similarly carry a bevel gear (not shown)located within a gear housing 17 conventionally rotatably carried by adrive shaft 18 vertically extending along vertical-axis l 1 between gearhousings 17 and 24. The upper (within 17) and lower (within 24) ends ofvertical driving shaft 18 might be conventional bevel gears wherebypowerablyrevolvable auger shaft 21'!" (through 24) revolves drivingshaft 18 which in turn (through 17) revolves sweep auger 30 aboutauger-axis 31.

The revolvable sweep auger 30 typically comprises an auger'shaft 31Textending longitudinally along its auger-axis 31 and hence radiatingoutwardly from bin vertical-axis 11 and rotatable gear housing 17. Therevolvable sweep auger 30 needs also to be provided with a capabilityfor concurrently angularly rotating about the bin vertical-axis, thisbeing customarily effected with a suitable traction means between thesweep auger and the bin floor 14. In this vein, prior art workers haveemployed the simple expedient of attaching a corevolvable circular wheel34 to the outward end 32 of shaft 31T. The circular periphery of wheel34 is notched or otherwise threaded and rests either directly upon binfloor 14 or upon a horizontal annular wear plate 142 carried by floor 14along the entire circular sidewall 12. Wheel 34 is of just sufficientdiameter to maintain the entire helical flighting 35 away from bin floor.14. Thus, as sweep auger shaft 31T and wheel 34 (both submerged in thegrain pile) co-revolve about auger-axis 31,'the grain-submerged wheel 34exerts a tractive effort which allows wheel 34 to travel annularly alongsaid wear plate. Inasmuch as traction wheel 34 and auger shaft 31T areco-revolvable, the entire sweep auger 30 is caused to also angularlyrotate about driving shaft 18 which lies along bin vertical-axis 11.Accordingly, for every 360 angular rotation of sweep auger 30 aboutvertical-axis 11, the entire lowermost stratum of the hereincross-sectionally circular lofty grain pile is helically fed inwardlytoward vertical-axis 11 and herein downwardly through bin floor centralopening 16 for further conveyance, as by unloader auger 20.

The preceeding description has been devoted to circulator grain binsgenerally of the prior art and including a representative (thoughnon-limiting) embodiment 9 thereof. More recently, circulator grain binsof larger circular diameters (e.g., 12) have become prevalent foreconomic and other reasons, which larger bins accordingly require morelengthy sweep augers 30. However, with more elongated lengths (andaccordingly weightier) sweep augers,-serious problems can arise. Priorart workers have long recognized the difficulty in making the elongateweighty sweep auger angularly rotate about the bin vertical-axis 1 1,while initiating the sweep auger powering from its inward end 33 only.Although such inward powering for auger revolvability has severalengineering and economic advantages, its ability to also angular rotateabout the bin vertical-axis is to a very large measure dependent uponthe revolving sweep augers underlying traction, e.g., the grainsubmergedco-revolvable wheel 34 with floor 14, plate 142, etc. Rotational forcesfor sweep augers have heretofore been restricted and confined to theinward end 33 and to the outward end (e.g., 12, 32, 142) of the sweepauger shaft 31T, it having been accepted axiomatically by prior artworkers (and adhered to herein) that attaching a traction wheel(e.g.,-34) to the helically flighted 35 medial major length of shaft 31Twould obviously impede grain flow therealong. Because grain flowimpedance along the sweep auger helical flighting 35 is to be avoided,the sweep auger traction means has heretofore been traditionallyconfined to one of the two ends (32 or 33) thereof, and usuallyprimarily to the outward end as with a co-revolvable wheel 34. However,with the increasing popularity of larger diameter bins and theaccordingly lengthier and heavier sweep augers, it becomes increasinglydifficult for the revolvable sweep auger to also angular rotate aboutthe bin vertical-axis when the sweep auger traction means is relegatedor confined only to the two auger ends. Especially pronounced is thisdifficulty when the grain conveyance mechanism is of type to exert onlymoderate torque upon the sweep auger inward end 33, as is the case withthe conventionally utilized sub-floor unloader auger 20.

With the improved underlying traction means, e.g., 50, of the presentinvention, which need not be confined or relegated to the two ends ofthe sweep auger, tractive effort and hence angular rotation for thesweep auger is greatly enhanced. In fact, as alluded to in theoppositely peering sectional elevation views of FIGS. 3 and 4, thetraction means improvement (e.g., embodiment 50) is preferablypositioned substantially intermediate the sweep auger ends (32 and 33)and isolated at consecutive medial pitches (353 and 354) of the sweepauger helical flighting 35. FIGS. 3 and 4 show the unmodifiedconventional auger helical pitches 351 and 354, respectively. As willnow be explained in FIGS. 5 and 6, the improved traction means 50 forsweep auger 30 comprises a plurality of separate distinct cogs 55extending radially externally from the helical edges 36 of theconsecutive medial pitches 352 and 353 of helical flighting 35 toprovide a segmented spiroid medial rim 55 for the sweep auger. Thesegmented spiroid rim 55, submerged within the grain pile, firmly abutsa substantially horizontal annularly roadway 51 that rests upon binfloor 14 and in completely surrounding relationship to bin vertical-axis61. Thus, annular roadway 51 is analagous to annular wear plate 142, buthas a much less diameter, depending upon whichever medial pitches of thesweep auger are provided with the segmented cogs array spiroid rim 55.

For each selected pitch of the sweep auger helical flighting 35, theouter edge 36 thereof is spaced an intra-pitch given mean-radius (whichis a substantially constant distance) from the auger-axis 31. There is aplurality of cogs 55 attached to at least two consecutive medial pitches(e.g., parent pitches 352 and 353) and including a cogs pluralityattached to one of said parent medial pitches, herein to helical pitch352. Each cog 55 extends radially externally from its parent flighthelical edge 36 whereby the free-edge 55A of each intra-pitch cog islocated a finite cog-radius from said edge 36 which is itself spaced anintra-pitch given mean-radius from auger-axis 31. Accordingly, thefree-edge 55A of each intra-pitch cog 55 is spaced the sum of meanradiusand cog-radius from auger-axis 31. Moreover, the several distinctlyseparated cogs 55 provide a segmented medial rim for the sweep auger,the array of separated free-edges 55A providing a generally spiroidouter contour that abuttably rests upon annular roadway 51. Assumingthat grain or other flowable particulate solids is loftily piled uponbin floor 14 so as to provide a surrounding flowable matrix for sweepauger 30 including spiroid rim 55, and also assuming that auger 30 ismade to revolve about auger-axis 31. Thus, the spiroid rim 55 abuttingannualr roadway 51 helps to maintain the auger-axis 31 in horizontallinearity and also churns through the flowable solids matrix, thecog-radius lead-face of each cog impinging against said grain matrixproviding traction sufficient to enhance angular rotation of sweep auger30. Yet this segmented cogs array, being located radially external tothe helical flighting outer edge 36, does not impede solids flow alongauger-axis 31 toward bin vertical-axis 11.

As best seen in FIG. 5, the free-edge 55A of each cog is preferablycurved and spaced a substantially constant cog-radius externally fromthe parent pitch helical edge 36. Moreover, the cogs attached to any oneparent medial pitch of the sweep auger helical flighting 35 arepreferably of identical size and shape and spaced at regular incrementsalong helical edge 36. Crosssectionally, the several intra-pitch cogsoccupy within the range of one-fourth to three-fourths the parent flightedge 36, and preferably within the range of onethird to two-thirds, saidratios permitting optimum traction within the flowable solids matrixwithout impeding solids flow parallel to auger-axis 31. In this vein, nomore than four (and preferably only two) medial pitches of flighting 35are provided with cogs, the width of underlying roadway 51 beingsubstantially equal to the longitudinal zone of the consecutive coggedpitches. Preferably, each separage cog 55 comprises a mounting-bracket56 and a lug 57, the mountingbracket 56 being welded or otherwiserigidly attached to its parent pitch edge 36. The lug 57, which providescog free-end 55A, is removably attached to mountingbracket 56, as withscrews 58 located radially remote of edge 36. This facilitatesreplacement of worn individual cogs during long term usage of thesegmented array of cogs, i.e., the sweep auger medial spiroid rimtraction means.

FIG. 5A, which is taken along line 5A-5A of FIG. 5 and passing throughauger-axis 31, aptly shows the cog-radius, the attachment of themounting-bracket 56 to the parent pitch helical edge 36, and theremovable attachment of lug 57 to mounting-bracket 56 with screws 58.

From the foregoing, the construction and operation of the tractionarrangement mechanism for rotatable sweep augers will be readilyunderstood and further explanation is believed to be unnecessary.However, since numerous modifications and changes will readily occur tothose skilled in the art, it is not desired to limit the invention tothe exact construction shown and described, and accordingly, allsuitable modifications and equivalents may be resorted to, fallingwithin the scope of the appended claims.

I claim:

1. In a circulator type bin for storing grain or other flowableparticulate solids and including upright sidewall means surrounding anupright vertical-axis and also a substantially horizontal bin floorintersecting said vertical-axis, said storage bin also including anelongate sweep auger that axially extends along a substantiallyhorizontal auger-axis that radiates outwardly from the bin vertical-axisand is located immediately above the bin floor, said outwardly radiatingsweep auger comvertical-axis, said sweep auger at pitch spacings alongthe auger-axis comprising helical flighting having a helical externaledge spaced an intra-pitch given meanradius from the auger-axis, theplurality of helical flighting pitches including an innermost pitch, anoutermost pitch, and, at least four consecutive medial pitches, theelongate sweep auger being revolvable about its auger-axis wherebyparticulate solids stored atop the bin floor are adapted to becirculated by the auger helical flighting inwardly toward the binverticalaxis, the improvement of traction mechanism arrangement for thesweep auger and comprising:

A. A plurality of cogs attached to at least two consecutive medialpitches of the sweep auger helical flighting and including a pluralityof cogs attached to one of said medial pitches, respective cogs having afree-edge located radially externally from the helical edge a finitecog-radius, said arrayed distinctly separated cogs at their free-edgesarray defining a medial rim of generally spiroid segmented contour andsubmergible within the stored flowable particulate solids; and

B. A substantially horizontal annular roadway surrounding the binvertical-axis and abuttably underlying the spiroid cogs array medial rimwhereby the axially revolvable and angularly rotatable sweep auger isstably supported above the bin floor thereby assuring that a finitespatial gap exists between the bin floor and the cog-free medial flightsof the sweep auger and also providing traction as the revolving distinctcogs churn through said flowable solids matrix environment.

2. The traction mechanism arrangement of claim 1 wherein the cogsattached to any one medial pitch of the sweep auger helical flightingcross-sectionally occupy within the range of one-fourth to three-fourthsthe external helical edge of its parent medial pitch whereby the cogs donot impede grain flow axially along the revolving sweep auger.

3. The traction mechanism of claim 2 wherein the cogs occupy within therange of about one-third to twothirds the helical external edge of theparent medial pitch. v

4. The traction mechanism of claim 3 wherein the cogs are of like sizeand shape and spaced at regular increments along the parent pitchhelical external edge, each cog being provided with a curved free-edgelocated said cog-radius from the parent pitch external edge.

5. The traction mechanism of claim 4 wherein only two consecutive medialpitches of the sweep auger helical flighting are provided with saidseparated cogs.

6. The traction mechanism arrangement of claim 1 wherein each cogcomprises a mounting-bracket and a lug, the mounting-bracket beingwelded to its parent flighting pitch at the helical edge thereof and thelug being removably attached to the mounting-bracket remote of saidflighting helical edge to facilitate replacement of worn cogs to ensurelong-term use of the spiroid medial rim traction means.

7. The traction mechanism of claim 6 wherein the cogs are of like sizeand shape and spaced at regular increments along the parent pitchhelical external edge, each cog being provided with a curved free-edgelocated said cog-radius from the parent pitch external edge having saidmean-radius.

8. The traction mechanism arrangement of claim 1 wherein thesubstantially horizontal annular roadway is substantially circular andhas a width comparable to about two medial pitches of the sweep augerhelical flighting.

1. In a circulator type bin for storing grain or other flowableparticulate solids and including upright sidewall means surrounding anupright vertical-axis and also a substantially horizontal bin floorintersecting said vertical-axis, said storage bin also including anelongate sweep auger that axially extends along a substantiallyhorizontal auger-axis that radiates outwardly from the bin vertical-axisand is located immediately above the bin floor, said outwardly radiatingsweep auger commencing at an inward end being pivotably associated withthe bin so that the sweep auger including its outward end is adapted torotate angularly about the bin vertical-axis, said sweep auger at pitchspacings along the auger-axis comprising helical flighting having ahelical external edge spaced an intra-pitch given mean-radius from theauger-axis, the plurality of helical flighting pitches including aninnermost pitch, an outermost pitch, and at least four consecutivemedial pitches, the elongate sweep auger being revolvable about itsauger-axis whereby particulate solids stored atop the bin floor areadapted to be circulated by the auger helical flighting inwardly towardthe bin vertical-axis, the improvement of traction mechanism arrangementfor the sweep auger and comprising: A. A plurality of cogs attached toat least two consecutive medial pitches of the sweep auger helicalflighting and including a plurality of cogs attached to one of saidmedial pitches, respective cogs having a free-edge located radiallyexternally from the helical edge a finite cog-radius, said arrayeddistinctly separated cogs at their free-edges array defining a medialrim of generally spiroid segmented contour and submergible within thestored flowable particulate solids; and B. A substantially horizontalannular roadway surrounding the bin vertical-axis and abuttablyunderlying the spiroid cogs array medial rim whereby the axiallyrevolvable and angularly rotatable sweep auger is stably supported abovethe bin floor thereby assuring that a finite spatial gap exists betweenThe bin floor and the cog-free medial flights of the sweep auger andalso providing traction as the revolving distinct cogs churn throughsaid flowable solids matrix environment.
 2. The traction mechanismarrangement of claim 1 wherein the cogs attached to any one medial pitchof the sweep auger helical flighting cross-sectionally occupy within therange of one-fourth to three-fourths the external helical edge of itsparent medial pitch whereby the cogs do not impede grain flow axiallyalong the revolving sweep auger.
 3. The traction mechanism of claim 2wherein the cogs occupy within the range of about one-third totwo-thirds the helical external edge of the parent medial pitch.
 4. Thetraction mechanism of claim 3 wherein the cogs are of like size andshape and spaced at regular increments along the parent pitch helicalexternal edge, each cog being provided with a curved free-edge locatedsaid cog-radius from the parent pitch external edge.
 5. The tractionmechanism of claim 4 wherein only two consecutive medial pitches of thesweep auger helical flighting are provided with said separated cogs. 6.The traction mechanism arrangement of claim 1 wherein each cog comprisesa mounting-bracket and a lug, the mounting-bracket being welded to itsparent flighting pitch at the helical edge thereof and the lug beingremovably attached to the mounting-bracket remote of said flightinghelical edge to facilitate replacement of worn cogs to ensure long-termuse of the spiroid medial rim traction means.
 7. The traction mechanismof claim 6 wherein the cogs are of like size and shape and spaced atregular increments along the parent pitch helical external edge, eachcog being provided with a curved free-edge located said cog-radius fromthe parent pitch external edge having said mean-radius.
 8. The tractionmechanism arrangement of claim 1 wherein the substantially horizontalannular roadway is substantially circular and has a width comparable toabout two medial pitches of the sweep auger helical flighting.